The present invention relates to an elastomer mixing unit, especially a mixing unit for rubber and rubber mixtures, with a mixing chamber, one or two rotors arranged in the mixing chamber and having shafts that penetrate the sidewalls of the mixing chamber, respectively, its housing. An inlet opening that is closed off is provided at the top. An outlet opening that can be closed off by a flap is provided for removing the mixed material. The mixing unit has one or more connectors for a suction line or a compressed air line for affecting the pressure within the mixing chamber.
In certain situations it is expedient to produce rubber mixtures in a vacuum or to perform mastication of natural rubber at increased air pressure. It is known to evacuate the mixing chamber with a suction line by providing suction within the area of the closeable inlet opening of the mixing unit. This type of mixing is, however, unsatisfactory because the rotor shafts must be positioned exterior to the mixing chamber and must be driven exterior to the mixing chamber. The required penetration of the sidewalls of the mixing chamber, respectively, of the mixing chamber housing and the thus resulting leaks prevent a sufficiently great pressure difference relative to the atmosphere.
It is therefore an object of the present invention to provide a mixing unit of the aforementioned kind with which in the mixing chamber a sufficiently high pressure or vacuum can be produced with simple technical means.